Adequate nutrition is essential for normal growth and development. During the lifetime of an individual, the growth during adolescence is faster than any other time period except during the first year of life. The phenomenal growth that occurs in adolescence, the pubertal spurt, creates increased demands for energy and nutrients (Jacob & Nair, 2012, January; 79 Suppl 1:S84-91).
Thus, nutrition plays an important role in pubertal growth. When a child or adolescent becomes malnourished, growth, including pubertal growth, will be attenuated. Adolescence can be the second opportunity to catch up growth if environmental conditions, especially in terms of nutrient intake are favorable. Therefore, adolescence is considered to be a nutritionally critical period of life (Jacob & Nair, ibid).
The nutritional needs of males and females are similar in childhood. However, after the onset of the pubertal growth spurt, there is a divergence. The reasons for this difference in nutrient requirements include earlier maturation of females and variations in physiological needs for some nutrients like protein, iron and B-vitamins. In addition to the weight and height differences, boys gain more muscle mass than fat compared to girls. Also, boys experience increased linear growth to produce a heavier skeleton and develop greater red blood cell mass than girls. Girls, on the other hand, accumulate more fat than muscle tissues. Overall, these differences in physiology have important implications for nutritional needs of male and female adolescence.
Growth is the fundamental physiologic process that characterizes childhood, and adequate nutrition is crucial for normal growth. In a rapidly growing child, there is an increased need for “building material” for the newly synthesized tissues.
Height as a growth parameter is measured as a linear stature at a single point in time compared to expected norms. The norms are typically provided by the general population as depicted in growth charts consisting of a series of percentile curves that illustrate the distribution of selected body measurements in children (for example, the charts of the Centers for Disease Control and Prevention (CDC)). Growth can be worrisome along two variables: height (short stature) and velocity (growth failure).
Protein-energy malnutrition (PEM) is the most important nutritional disease in developing countries because of its high prevalence and its connection with increased morbidity and mortality in all age groups as well as impaired physical growth and mental performance. Associated deleterious effects on physical and mental growth and maturation have been demonstrated in experimental animals and they seem to occur in humans. Nevertheless, one cannot dissociate completely the nutritional factors from other environmental conditions, or to ascertain irreversibility of the consequences of malnutrition.
In developed countries, where plenty of variable food is available, fat and carbohydrate intake of short small for gestational age (SGA) pre-pubertal children was found to be significantly lower compared to the recommended daily intake or dietary reference intake (DRI) for age-matched children (Boonstra et al, 2006, Horm Res, 65:23-30). In addition, the caloric intake of children with idiopathic short stature was positively correlated with growth velocity both before growth hormone (GH) treatment and during the first year of GH treatment (Zadik et al, 2005, Pediatrics 2005; 116(1): 68-72).
The factors that influence energy needs of adolescents are activity level, basal metabolic rate and increased requirements to support pubertal growth and development. Adolescent males have higher caloric requirements since they experience greater increase in weight, height and lean body mass than females.
The protein Recommended Dietary Allowance (RDA) for adolescents is 0.8 g/kg body weight, with a large acceptable range between 10%-30% of the total daily energy intake (DRI, 2005). Adequate protein consumption is essential to meet the growth requirements and maintenance of existing lean body mass and accrual of additional lean body mass during the adolescent growth spurt (Beckett et al, 1997; European Journal of Clinical Nutrition 2000; 54(Suppl. 2): S52-9). When protein intake is consistently inadequate, reduction in linear growth, delay in sexual maturation and reduced accumulation of lean body mass may be seen (Torum & Chew, ibid).
Micronutrients are nutrients required only in minute amounts by the human body, that nevertheless play a critical role in the normal growth and development of the body. Deficiencies in micronutrients can lead to a breakdown in numerous bodily functions and result in a plethora of mild to severe disorders. Since the human body is not capable of synthesizing most of the essential micronutrients, the only way to obtain them is through dietary food sources or through supplementation.
The principal micronutrients fall into two categories—vitamins and minerals. Vitamins are essential micronutrients that the body is not capable of synthesizing in sufficient quantities for its growth and maintenance and have to be derived from dietary food sources. However, most vitamins are present only in minute quantities in the foods that we ingest and their bioavailability depends on the food source. There are thirteen essential vitamins of which four, A, D, E, and K are fat soluble and nine, B1, B2, B3, B6, B12, pantothenic acid, biotin, folic acid, and C are water soluble. The fat soluble vitamins are capable of being retained in the body while the water soluble vitamins are excreted from the body.
Minerals which form the second category of micronutrients are inorganic in nature and can be broken down into two sub-categories: macrominerals such as calcium (Ca), phosphorous (P), sodium (Na), potassium (K), magnesium (Mg), and chloride (Cl) and trace minerals such as iron (Fe), zinc (Zn), iodine (Io), selenium (Se), copper (Cu), manganese (Mn), fluoride (fl), chromium (Cr) and molybdenum (Mo). Just as with the essential vitamins, these mineral micronutrients are essential for bodily functions and cannot be synthesized by the body. Therefore, it is necessary to have an adequate intake of these mineral micronutrients from food sources or through supplementation.
Several micronutrients including zinc, iron and vitamin A have been shown to play a critical role in normal growth. The most conclusive evidence to date linking the intake of a specific micronutrient to child growth is for zinc, though the mechanisms by which zinc deficiency impairs growth has not been elucidated. Iron deficiency is associated with anemia and impaired physical growth, but iron supplement alone had no significant effect on child growth (e.g. Ramakrishnan U et al., 2004; Journal of Nutrition; 134: 2592-602). Several observational studies reported significant correlations between vitamin A status and stunting (Fawzi W W et al., 1997, Epidemiology; 8: 402-7; Kurugol Z et al., 2000, Paediatrics Perinatal Epidemiology 2000; 14: 64-9). However, a later Meta analysis by Ramakrishnan et al. (2004, ibid) concluded that vitamin A supplementation interventions had no significant effect on growth.
Most of the studies which explored the role of specific nutrients in growth and the effect of supplements enriched with these nutrients have focused on malnourished children populations in developing countries.
The effect of a commercially available nutritional composition (PediaSure®) on weight-for-height measurements have been examined in children age 3-5 years with picky-eater behaviors in the Philippines and Taiwan. The supplement is designed to provide complete balanced nutrition for children 1-6 years. However any influence of any kind of combinations of micronutrients on linear growth in short stature adolescents has not been evaluated and no such nutritional composition is commercially available.
There is an unmet need for, and it would be highly advantageous to have a nutritional supplement specifically designed to enhance the linear growth of pre-pubertal adolescents who are significantly shorter and leaner than the norm and that also affects the pubertal growth spurt of these adolescents.